Philosophy

6

LECTURE: Jackson’s knowledge argument and property dualism

An argument that is related to Nagel’s “bat” argument, and that has also gotten much attention among philosophers and scientists interested in the question of whether science can explain consciousness and qualia, is due to philosopher Frank Jackson. It’s sometimes called the “Mary argument” and sometimes the “knowledge argument,” for reasons that will become evident. Here’s Jackson:

I know something Mary doesn’t

The “Mary” thought experiment

Jackson asks us to imagine Mary, a scientist who lives at some future time when we have learned everything there is to know about physics, chemistry, biology, neuroscience, and the physiology of perception. Imagine that Mary is brilliant (with a photographic memory, etc.) and has mastered this whole body of knowledge.

But let’s also imagine that Mary has, for whatever reason, lived her entire life in a black and white room, and has never been allowed to have any visual experience of colors. She’s never seen red, blue, green, yellow, etc., but only ever black and white. The books she’s read, the clothes she wears, the objects in the room around her, the TV screen through which she communicates with the outside world, etc. are all black and white. Perhaps she’s even had to wear some special goggles that filter color out.

Still, during this whole time, she has come to learn all the relevant scientific information about what happens when someone does see colors. For example, she knows all about the way the surface of a red apple absorbs some wavelengths of light and reflects others, the way this affects the retina in the eye, the way the brain processes the information it gets through the optic nerves, and so on. She can tell you about all this down to the smallest detail. She knows all the relevant facts about the physical world – about the physics, physiology, etc. of the situation – that there are to know. But she’s never herself seen red.

Now imagine that Mary is released from the room and sees a red object herself for the first time. Does she learn something new? Yes: She learns what it’s like to see red. And yet, before her release from the room, she did not know this, despite knowing all the physical facts about the situation. And what that shows, according to Jackson’s argument, is that physicalism or materialism is false. Why?

She’s wearing a red dress… but has never seen red!

The argument

Here’s the argument Jackson bases on this thought experiment:

1. Physicalism (or materialism) holds that the physical facts are all the facts there are.

2. But before she was released from the room, Mary knew all the physical facts there are.

3. And yet, before her release from the room, she did not know all the facts there are, because she learned something new after leaving the room (namely, what it is like to see red).

4. Therefore, the physical facts are not all the facts there are, because there are further facts (such as the fact about what it is like to see red) that would remain unknown even when you know all the physical facts.

5. Therefore, physicalism (or materialism) is false.

Now, the facts that Mary learns when she leaves the room are facts about the qualia that are characteristic of conscious experience. So, these facts, the argument concludes, are non-physical. This entails a kind of dualism. (What kind? We’ll come back to that in a moment.)

Jackson formulates the argument in terms of visual experiences of colors, but the same sort of argument could be framed instead in terms of any of the five senses. For example, you could imagine that Mary has never heard sounds, but has mastered all the scientific knowledge there is about what goes on in the brain, the eardrum, the surrounding air, etc. when people hear sounds. And then she leaves the room and hears a sound for the first time. Such arguments could be given to show that all qualia are non-physical.

Like Nagel’s argument, and like Malebranche’s argument, you can read Jackson’s argument as grounded in considerations about the sort of knowledge that science confines itself to. If science is going to treat the physical world as something that can be entirely described in terms of the language of physics, chemistry, etc., where all of this knowledge is the kind that can be written down in textbooks and the like, then it is inevitable that knowledge of what experience itself is like is going to be left out. Science’s conception of the physical world seems inevitably to make consciousness non-physical.

The zombie argument

There are several other arguments in recent philosophy of mind that have a similar lesson. Let’s briefly look at one more of them. It’s called the “zombie argument” and is associated with the contemporary philosopher David Chalmers. Here he is:

Not a zombie

Here’s one way to understand Chalmers’ argument. Consider that, for a materialist, you can give a complete explanation of everything we say and do in terms of nothing more than cause and effect relations between physical entities. For example, if Ted cuts his finger on a tack and lets out a scream as a result, you can explain that entirely in terms of the way the skin of his finger was damaged, nerves sending a signal up his arm to his brain, neurons subsequently firing which cause other neurons to fire which cause other neurons to fire, muscles flexing and his jaw moving while air went out from his larynx, and so on.

You never have to make any reference to what was going on in his thoughts or conscious experiences. Of course, the materialist would say that the thoughts and conscious experiences are just brain activity, but the point is that you don’t need to say anything about them in order to explain what happens. You could just make reference to neurons firing, muscles flexing, etc.

Now, imagine a world filled with creatures that are exact physical duplicates of us, down to the last particle. Their brains are wired like ours, their muscles are structured just like ours, etc. As a result, they act exactly like we do: They walk and talk like we do, scream when injured just like we do, give philosophical arguments and write love poems just like we do, and so on. The difference is that they have no consciousness or qualia whatsoever. It’s all nothing more than unconscious physical cause and effect – again, neurons firing, the muscles flexing, and so on.

If you were transported to this imaginary world, you’d never know that these creatures were any different from us, because they would act exactly as we do. The reason they would is, again, that their brains, bodies, etc. are physically constructed and operate just the way ours do. And materialists themselves say that such physical construction and operation is sufficient to explain everything that we do.

The idea of a creature that is physically identical to us but lacks any consciousness or qualia at all is what philosophers call the idea of a “zombie.” Obviously, zombies in this sense are not the lumbering, ghastly, undead creatures of horror movies. Those sorts of creatures do not act like normal people (the way that “zombies” in Chalmers’ sense do act like normal people, despite lacking qualia and consciousness).

“Wait, you’re not talking about me?”

The argument Chalmers’ bases on this thought experiment basically goes like this:

1. Materialism claims that the physical facts are all the facts there are.

2. Now, in our world, there are conscious experiences.

3. But in theory, there could be a world (i.e. a “zombie” world) with creatures that are physically and behaviorally identical to us, but entirely lacking in any conscious awareness.

4. Therefore, the facts about conscious experience are further facts about our world, over and above the physical facts about us.

5. So, materialism (which, again, claims that the physical facts are all the facts) is false.

Property dualism

The kind of dualism that arguments like Nagel’s, Jackson’s, and Chalmers’ are often used to defend is not Descartes’ substance dualism, and not Aristotle’s and Aquinas’s hylemorphic dualism, but a third kind of dualism called “property dualism.” We can define it as follows:

Property dualism: the view that there is only one fundamental kind of substance, namely physical substance, but two fundamental kinds of properties, namely physical properties and non-physical mental properties

You can think of it as a kind of middle ground position between materialism on the one hand and Cartesian dualism on the other, and property dualists often seem to be thinkers who are broadly sympathetic to the basic worldview of materialism, but who feel the need to move away from it somewhat because of the difficulty it has in accounting for certain phenomena (such as qualia).

If we’re asking how many kinds of substance there are in the world, the property dualist would agree with materialism that there is only one kind: physical substances. Like materialists, the property dualist rejects Descartes’ idea that the mind is a res cogitans or immaterial substance.

But if we’re asking about the properties or attributes of substances, the property dualist disagrees with the materialist view that physical properties (such as the properties of matter that you’d see listed in a physics textbook) are all the properties there are. According to property dualism, some physical substances, namely brains, have non-physical properties in addition to their physical properties. To this extent, they would say, Descartes was right to hold that you cannot reduce mind to matter. And arguments like Nagel’s, Jackson’s, and Chalmers’ are claimed to show that qualia, in particular, are non-physical properties of the brain.

Now, because they are otherwise sympathetic to materialism, some property dualists (such as Chalmers, and Jackson at the time he came up with the “Mary” argument) are inclined to agree with materialism that our behavior can be entirely explained in terms of purely physical causal processes. These property dualists take an epiphenomenalist view about qualia, according to which qualia don’t have any causal impact on what we do. They’re just along for the ride, as it were. We’d act the same way even if we didn’t have them – even if we were “zombies.”

This yields a paradoxical result: If qualia don’t do anything, then they aren’t what is causing us to talk and argue about them (since, again, they don’t cause anything). So how are we talking about qualia, in that case?

We seem to be led into a bizarre impasse. On the one hand, the modern “mechanical” conception of matter seems to entail that consciousness cannot be material. And yet, if we think of it the way Cartesian dualists and property dualists do, then it seems that consciousness cannot interact with the body or have any effect on what we say or do. What is going on?

Miss me yet?

Contemporary Aristotelians would say that this bizarre result is a consequence of the “mechanical world picture” that defined itself in opposition to Aristotle, and indicates that it was a mistake to re-define matter in a way that leaves our commonsense understanding of color, odor, sound, taste, etc. out of it. But that is an issue we can return to after looking in more detail at one further aspect of the mind that has raised puzzles: intentionality. We’ll do that next week.

In the meantime, here are some YouTube videos exploring these matters in further detail:

Thinking Illustrated on the Knowledge Argument:

https://www.youtube.com/watch?v=TAXp_5LpnAI

Jeffrey Kaplan on Jackson’s “Mary’s Room” thought experiment:

https://www.youtube.com/watch?v=QhTRbXpfKw8

Interview with David Chalmers about zombies and consciousness:

https://www.youtube.com/watch?v=NK1Yo6VbRoo

Jeffrey Kaplan on Chalmers’ zombie argument:

https://www.youtube.com/watch?v=VLzmYjviDsk

Sally Latham on property dualism:

https://www.youtube.com/watch?v=cUJK8-Y8EPU